Bug 520685 - [Generic Editor] Sort ext. by most specialized content-typeI20170809-2000

Factorize extensions and registry polling (can be continued).
This allows most registries to return first the extension that applies
to the most specialized content-types.

Change-Id: Icfd5d0c2e72cd579e9fe8c034420d88c628f39a6
Signed-off-by: Mickael Istria <mistria@redhat.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/org.eclipse.ui.genericeditor/src/org/eclipse/ui/internal/genericeditor/GenericContentTypeRelatedExtension.java b/org.eclipse.ui.genericeditor/src/org/eclipse/ui/internal/genericeditor/GenericContentTypeRelatedExtension.java
new file mode 100644
index 00000000000..da7dc2be16c
--- /dev/null
+++ b/org.eclipse.ui.genericeditor/src/org/eclipse/ui/internal/genericeditor/GenericContentTypeRelatedExtension.java
@@ -0,0 +1,47 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Red Hat Inc. and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ * - Mickael Istria (Red Hat Inc.)
+ *******************************************************************************/
+package org.eclipse.ui.internal.genericeditor;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IConfigurationElement;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.content.IContentType;
+
+/**
+ * This class wraps and proxies an instance of T provided through extensions
+ * and loads it lazily when it can contribute to the editor, then delegates all operations to
+ * actual instance.
+ * 
+ * @param <T> the actual type to proxy, typically the one defined on the extension point.
+ */
+public class GenericContentTypeRelatedExtension<T> {
+	private static final String CLASS_ATTRIBUTE = "class"; //$NON-NLS-1$
+	private static final String CONTENT_TYPE_ATTRIBUTE = "contentType"; //$NON-NLS-1$
+
+	public final IConfigurationElement extension;
+	public final IContentType targetContentType;
+
+	public GenericContentTypeRelatedExtension(IConfigurationElement element) throws Exception {
+		this.extension = element;
+		this.targetContentType = Platform.getContentTypeManager().getContentType(element.getAttribute(CONTENT_TYPE_ATTRIBUTE));
+	}
+
+	public T createDelegate() {
+		try {
+			return (T) extension.createExecutableExtension(CLASS_ATTRIBUTE);
+		} catch (CoreException e) {
+			GenericEditorPlugin.getDefault().getLog().log(new Status(IStatus.ERROR, GenericEditorPlugin.BUNDLE_ID, e.getMessage(), e));
+		}
+		return null;
+	}
+}